Sheet feeding system with lateral registration and method for registering sheets

Abstract

A sheet feeding and lateral registration system, including feed rollers (41, 42) for feeding sheets (50) in a process direction and registration apparatus (52, 53) for registering each sheet in a direction laterally of the process direction. The registration apparatus includes a shifting system (53) for laterally shifting a carriage (52) on which the feed rollers are mounted. A single edge sensor (57) is arranged to provide a signal on detecting the presence of a sheet, and a control controls the lateral shifting system in response to that signal. The control is operated such that if the sheet (50) is not detected by the sensor (57) on initial entry of the sheet into the feed rollers, then the shifting system (53) is activated to move the feed rollers laterally towards the sensor until the sheet is detected by the sensor, whereupon the lateral movement is stopped. However, if the sheet is detected by that sensor on initial entry of the sheet into the system, then the shifting system is first activated to move the feed rollers laterally away from the sensor until the sensor no longer detects the sheet, and then the shifting system is reverse activated to laterally move the feed rollers back towards the sensor until the sheet is again detected by the sensor.

What is claimed is: 
     
       1. Sheet feeding apparatus including sheet feeding means for feeding sheets in a process direction, and registration means for registering the sheet in a direction laterally of the process direction; said registration means comprising shifting means for laterally shifting said feeding means a fixed sheet edge sensor providing a control signal on detecting the presence of a sheet in said sheet edge sensor, and control means to control said lateral shifting means in response to said sheet edge detection control signal, characterized in that: if a sheet is not detected by said edge sensor upon the entry of the sheet into said feeding means, then said lateral shifting means is activated to move said feeding means laterally towards said sensor until the sheet is detected by said sensor, whereupon said lateral movement is stopped;   but if the sheet is already detected by said same sensor upon the entry of the sheet into the feeding means, then the shifting means is first activated to move the feeding means laterally away from said sensor until said sensor no longer detects the sheet, and then said shifting means is automatically reverse activated to move said feeding means back towards said same sensor until the sheet is again detected by said same sensor, being approached from the same direction, to reduce hysteresis error, whereupon said lateral movement Is stopped.   
     
     
       2. The apparatus of claim 1, further including means for driving said sheet feeding means to drive a sheet in a first direction, stopping the sheet in said sheet feeding means to enable said registration means to register the sheet, and then reversing said feeding means to drive the sheet in a direction opposite the first direction. 
     
     
       3. The apparatus of claim 1, wherein said sheet feeding means comprises at least one pair of rollers mounted on a carriage, said lateral shifting means being connected to said carriage. 
     
     
       4. In a method of sheet feeding and lateral registration, including feeding sheets in a process direction with a sheet feeder, and registering the sheet in a direction laterally of the process direction; said lateral registration comprising laterally shifting said sheet feeder by sensing a sheet edge at a sensing position and controlling this lateral shifting movement in response to said sheet edge sensing, characterized in that: if the sheet is not initially sensed at said edge sensing position, then said lateral shifting is activated to move said sheet feeder laterally towards said sensing position until the sheet is sensed, whereupon said lateral shifting movement is stopped;   but if the sheet is already initially sensed in said sensing position, then the sheet is first shifted laterally away from said sensing position until it is no longer sensed, and then said sheet is automatically reverse shifted laterally to move back towards said same sensing position until the sheet is again sensed approaching from the same direction, to reduce hysteresis error, whereupon said lateral shifting movement is stopped.   
     
     
       5. The method of claim 4, further including driving the sheet in a first process movement direction with the sheet feeder, stopping the sheet in the sheet feeder to enable said sheet lateral registration, and then reversing the sheet feeder to drive the sheet in a direction substantially opposite said first direction.